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March 26, 1929. G. w. PICKARD ELECTRICAL CONDENSER AND PROCESS OriginalFiled May 12 1920 6 Sheets-Sheet 1 I avwemkoz merPic/baml 81 flfglttowmMarch 26, 1929. G. w. PICKARD ELECTRICAL CONDENSER AND PROCESS OriginalFiled May 12. 1920 6 Sheets-Sheet 2 3140c 'wfoz Gre enlmfWkiltierHc/Eard @513 GHQ: 11c 1 March 26, 1929. 6. w. PICKARD 1,706,816

ELECTRICAL CONDENSER AND PROCESS Original Filed May 12. 1920 6Sheets-Sheet 3 Gitenleqf Wfiiiiz'er Retard March 26, 1929. G. w. PICKARDELECTRICAL CONDENSER AND PROCESS Original Filed May 12 1920 6Sheets-Sheet 4 WWW W1 March 1929' G. w. PICKARD ELECTRICAL CONDENSER ANDPROCESS Original Filed May 12. 1920 6 Sheets-Sheet 5 saux mu gave "forMarch 26, 1929. G. w. PICKARD ELECTRICAL CONDENSER AND PROCESS OriginalFiled May 12. 1920 6 Sheets-Sheet 6 Patented Mar. 26, 1929.

arren srarss.

GREENLEAF \VBSITTIER PiCKARD,"OF NEWTON CENTER, MASSACHUSETTS}'ASSIGNOR'TO WIRELESS SPECIALTY APP'AEA us CORPOR TION E, NEW YORK.

COMPANY, 0E BOSTON, MASSACHUSETTS, A

' EL CTRICAL CONDENSER AND PROCESS.

A ucauonmeama 12, 1920, Serial is. $86,919. Renewed February '26, 1927.

- This inventionrela tes.to improvements in processes. and apparatus formanufacture of electrical condensers of thesheet type and f moreparticularlyofthe type wherein mica is used for the dielectriesheets..-;;The' object of theinvention is to obtain ran improved condenserofjthe -she et;type, which-comprises a stack-consisting as nearly,aspossible}; of {only -;alternately-disposed sheets of mica;-andfmetalfoil in permanently intimatecontaet with each other, the -inte rior ofthe stack betWjeenthe sheetsbeing freed as nearly as possible of air,moisturev the latter. being ,heated; i

and all materialscther than. the mica and foil sheets. tl1emselves,.themica. andg. .foil sheets hav ng .noth1 1 1g whatsoever;between.

them when th;e; .obj.cct of. the invention: is

coinpletely-.- attained. The :foils adapt-ed for. gmy, pr oeessesare-preferably SQf.l3 fiIld.IlQl1- j resilient so that;.asthe nesult otthe execue .ti n .ot e.prec ssjth yrare l t me 901111 .tact withthemicasheets; their surfaces ill-j. id estaeketshe b ng e f numberof... the selections got. the; material- ..smck led l' t d fiem'e'eehifaces anaqgnnieetd tbg etlier m ser'ies .to coni ,mois ture andvvaa Iand-sealed; from the ,out-. 5' side, atmosphere. ;'I here f ore Iprefer. lead s i .(se t m s k ew s ii f ,trad e') ,falthou h not only.maytherebe used:

1- s tzm t l; tQi-J jl iQ L P-PQT .tlii lter puahz to be sufficientlynon-resilient,-.but,.tl1e foils Q themselves may .have some, degree ofresili- 1 :ence althoughg that is not g$0' desirable,

.-.char:1cterg ofgsuchfoil sheets, they exert no tcndcncyto force,theshccts apart after they have been compressed together, and thercsultantcondensers Wlll consist of mica and foil sheets compressed.into persistently intinulie Contact with each" other without any mzl.lantial intervention. ofwan whichlms tion of the process of constructionas an agent for washing, out air and moisture from I betr on the sheets.The condenser is -permanently compressed mechanically to main- -15 tainthe above COIlClltlOIl. and to the same end permanently embedded in amass of suitablev paraffin; the. condenser prior tozsuch ,cmbeddingbeing sulnected to the highest practicable. compression, so. that ,the.treat 5e ment during manufacture and the permanent compressing andembedding I serve respec tively to eliminate froinand prevent re-entryintothe interior :of the stack of materials foreign. to the mica and folgsheel's.

Ring iframe exi tfid between th e sheet's during the eziecu-f Theinvention consists injc'ertain of the stepsof the processes describedherein and ,in certain .combintion's of {such-steps, in the [improvedcondenser itselLT-and in certain features of apparatus mp1oyed, ,au s'will Figl (i is. an: elevation showy g} lthe' coins .pr e'ssio n of thematerial-stackin the pressafter removal from the bath .of

. Fig. .7,is ,elevationof part of u etmaterial-stack .which .has been.selected there from. for use in or as a. condens eij staclc Fig' 8 san'; e1 ev,auoa or assem led condenser stac'k fmf condenser consisting.of a or'E eiicjaia n' mba-baaga em anthe end b ea aw- Qwing. ,tothe;soft inertpor. non-resilient .,dotted.lines, Fig.19) a s in sertedin todts perinanent container or casing, the: condenser an, d casingbeing highly, .comp ressecltogether ;in a spring press inFig. 9-,{andatemporary ialsehead beingi sec u redlto the top .of the casing. f

, Fig. 11 isla detail offlthe leafv spring forming apart of the press oiFig.9. l

Figfli is an elevation showings form of permanent spring clamp ,for thecondenser.

F ig.. 13 diagrammatic planoflappm ratus involving a vacuuin tank in.which is inserted-the apparatus of Fig. 9. and "a wax -reservoir orparaffin tank connected by pipes to the vacuum tank for the purpose offilling thecondenser easing with embedding, paraflin.

Fig. 14: is an elevation of appa-rtaus employed in the special processof cooling the embedding .parafi in in the'condens r casing.

' Fig. 15 is an elevation, partly in section, of the condenser casing ofFig. l.0.containing the einbeclment and condenserpwith casing coi er inplace.

. While aiiy ltiiid -o t wart o'i Tsiniila r Int (lethal may be employedin this inventioinneverthe less parufiin vax is very highly preferableas being specially adapted to the gnoeesses and product hereof. Also asmall percentage (say five per cent more or less) of carnauba wax orwaxes possessing'similar properties is mixed with the paraffin. Theaddition of the carna ub a vim the "melting point of the mixture andwhen cooled provides a ha'rilet niiitelrial ferth'e condenser"eir'ihediiieiit. This "specification of "wait refers to the wax usediii 'aIl the steps "ot the 'j'roc'esses. wherever tfefeiite is 'liererha'ftdit0 parafih1"a ltine,it is'f'to be "undei'stood as 'ip'r'eferablyinclfitlingthcsitiall perc'enti-i ir'eot car- 'Tiiiiibi wax. The waxilscd in all the proi. sscs hereof is preterably ie-watery iirmn moisture-asby'heatingitto froin 100 centit rdde'toism "C. M The condenset'stnatleby 'tlie pi'ocesse ereare "n'i'oi'e' 'ii-rtichlarly atlaptetl fbi use"iintlc'ncdntliti 'it is fiflrptiititht that there shall be miniih'urtiel'e'ctiicallb'sses in the condetise'r in ervice's: itii'atliotelegraph'tthhitiitt'ers 61 iii "powct lines, laboratory standards antl theli'keTlieeontleii'ser seek, in any case, may be employed as a unit in any"desired way,6r it Iniiybeconstructed in sections whielFnuiy begirtihped ih'serVi'ce in any desired reldtionfbfsrie's, parallel orseriesparallel, or the eond'fis'r' ftiay bec iinstriicted intofs'ectionspermanently connected i'n'sel' ics, 'zis in the radio telegraphtransmitting use e ite-i t'he coil(liifsr is not oiil constructedwithseetieti's iiisi lat etl fremcne' another; at their end faces, thewell-k iiown way, but the sections are "permanently connected in seriesin the well-known manner via foils projecting frtimthe'stack-sides.

Inkpre'pai'atiiihforthejprocesses, the sheets of'niica and toihare' 'cutto whatei-er sizes Iii'ayhe desired rm a particular design of coudehser,'i'hdfoil sheets beiiiig usually longer and harrowerthan the mica sheetsas in the culinary sheet condenser. The toil sheets are wlled to beperfectly flat, and the mica. sneets are tested, dried. and storedih'air-tiigiht coutainers to await execution ofthe processes-1. As thefirst process, allthe sheets, of both mien-end foil, arec'oa'ted withthe pai'allin 'which'serves lati asail'el'crfJeht for-hashing riiitziirand inoistiite 'troin hetween the assemhled sheets,later steps being:employed for the purpose of squeezing outthis paraliin fi-mnhetu'een'the slieetst'o the gr atest poss ble eiztentwith the View of"l"e:ivin.9; a condenser stack consisting only of the sheets of micaan'dloil, preferably freed frbniall the par'afiin whichhas beentemporarily niployed for the purpose of Was-inn} out the other undesiredfoi eig ji in:iteriiils,"i. air and nioisone. This bearish-may be donehytreiiting the loosely-assembled sheets' to a heth oi hot paraflin; butthe greatly preferred process is that o' t separatelycoating each sheetwith the parafiin, this being done preferably While the processofbuilding up the material-stack out of the separate sheets is beingeffected, this preterenee beiiifg' due'to the 'tactthat the sheets udienivet ii'ithpai'a'fiinaie "much more conveniently held together at thisstage of the processes than when dry. At this stage, thest'ac'ki's'called 'the material-stack because it constitutes the material outof which the dvtittia'l condenser 's'tac'k (or simply condenser) istob'e' made as by sele'ct'ing'a sufiicieht "length 'or Inegths of the'iuateriahstack 'ithichh'as or liave electrical capacity suitable forthe condenser.

Fig. 1, in "elevation, shows the building stand consisting ofhorizerital metal plate 1, two eerie-a1passa e-the rear. each-of theseposts being-eat away at-8 to alihe'and guide he sheets of'1ni'ca=tlurinf1 the'operation of building the material-stack,and fourlegs l'a'reprovided on the bottom 1.

Figs. 2 and. 3 show the building stand of Fi 1' inserted in a waxingtray'5, the latter bciiifi heated by a. very mall lhinseh burner -6(Fig.3) tofkeep simpl warm the paraflin intlie tray. Ilhstbetore eachsheet of In'icaor foil is'plac'ed first on top of thebase 1 and then ontop of oneanother alternately, the operator dips eachsu'ch sheet intheparaffin in tray '5- and then places it onthe growing stack shown'inFigs? and 3. 'As stated, the

cut away portions of posts 2 aline the mica sheets 7'asishewn in Fig. 2.Then'ontop 0t each coated niiba sheet ispla'ced a co'ated foil sheetas8,'the tirst foilsheetb'eing'placed say so thatits leftfiroj'ectstothe left (it the mica sh'et 7, but at its right it does not extend to'tl'ieedgc Git-he inicasheet 'i. Then another coated r'n'ica sheet-isplaced exactly on topof the first foil sheet 7. heing alined therewithby the cut away portions 3 of the 'posts Then the 'ne'xt. coated foilsheet as 9 is'placed on top of the lasti'nica. sheet llut extending tothe right beyond the mica sheet and at its left not. extend ing to theleft end of the mica sheet. As'the operator puts each foil sheet inplace, she cana'iid should ol'rservc Whether any air bubble is entrainedin the parailin (due possibly to incomplete dipping), and it there be,or preferably in ever ease,'she su'ioeths down (squeegees) each foil tosqueeze out the air. Likewise, in pet-ting each dipped mica sheet inplace, she prcsses it dawn on the coated foil sheet beneath it, for thesame purpose of squeezingout air. Thus the material-stack is built upofalternated sheets of mica and toil, while the si1cce's sive'f0ilsheets are placed so as to'eritend respectively at opposite ends of thestack and overlap one another (although separated'by a mica sheet) inthe central part (lift 1B'illfiSiOfltllG mica sheets in the stack."lhehott oin "1 of the building stand (Figs. 1 and 2)"is set down in thebody of liquid paratfin in tray 5, so that it is heated by the parafkeptwarm, i. e., both by the Warm coatings I on the respective sheets and bythe heat conducted from the warm parafiin in tray by the metal base 1and metal'posts 2and conducted upwardly'by the growing stackjitself.This maintenance of warming. during building assists in keeping #downunnecessary thickness of; the :coating paraffin 1 between sheets (due totheincreasing tendency of the 1 growing stack to squeeze out excesspa'raflin. by gravi-ty)-' and-also assists in tending to av'oid'theentrapping of air'inlthe stack at this stage (due to the tendencytogreater intimacy of the sheets and theconsequent tendenc'y ftocause-the liquid parafin to wash out --air' and moisture from betweenthe sheets rather than to permit entrance or entrapping betweenthe'sheets).""-If the material-stack during the'building operation becomesinsufficient-ly Warm, orif it hardens'as appears to the operators eye,she may spoon up parafiin from tray-5 and pour it over the materialstack from{ti'me to time fo'r'thef purpose of keeping warm andsoft theparaffin between the-sheets. J: ;.:a p

Tli'e "material-stack may be bu1lt-completely undera bath-ofl'pa'rafiin, but as described above it is usuallybuilt-in atmospherewith its lower end "in heat; conducting relationwith'the parafinintrayfi, which causes less exposure of the'ope'rators fingers to theheated Y paraflina lt' is i immaterial that the small corner's oredgesof the .sheets which are held in'gthe operators fingers during thedipping operation be not-coated with the paraffin, for the dipping andbuilding operations'leave suflicicnt paraifin' on thefsheet's s0that-inthe building operation itself and espe cially during thesubsequent squeezing or washing out operation the entire surfaces of thesheets are washed of air and moisture hy the outgoing-paraflin, it notbeing the object of the invention to retain-any paraffin permanently onthe sheets. 'Ihe'temperature of the parafiin in building tray 5 duringthe coating and building operation 'is'about centigrade, i. e., aboutthe temperature the operators fingers will conveniently stand.

During the building operation, in case the eventual condenser is toconsist of a number of separate sections, temporary section separatorsof metal or any other desired material may be inserted 'as a convenientmethod of separating the sections in the materialstack, particularly ifduring the building operation pains are taken to insure that eachsection has the same electrical capacity, as by using material ofuniform thickness for the :mica sheets and byinserting the temporary ingat substantially separators or markers above the same number of micasheets for each section.

After the imiterial-stack is built to the capacity of the building standof Figs. 1, 2 and :5, it is allowed to cool therein sufficiently topermit convenient handling without impairing the unitary character ofthe stack consisting of the sheets temporarily held in alinement by theparaliin coatings, and then transferred to the so-called pressing frameshown in Fig. 4. .This frame consists of a substantial metal base 10with four upright metal posts 11 at the four corners thereof. Each ofthe four posts 11 is provided with cut away portions 12 like the cutaway portions 3 of the posts 2 of Fig. l, to aline the four corners ofthe mica sheets in the stack. When the n'iaterial-stack is inserted inthis pressing frame, the foil sheets project out-at bothends of thestack between the vertical posts 11, the cut away portions 12 of theposts 11 serving to hold all the mica sheets in alinement as stated.After the materialstackis inserted in this pressing frame, a plate 10'with four holes for the four posts 11 is slipped down over. the saidposts and upon the top of the stack. On plate 13 is placed a plate 13between the posts 11, to serve in a later step as a temporarycompressing member on the stack, the base 10 of the pres. g'framc. Thisplate 13 has a central depression 13 for use in manner to be describedlater.

The next step consists in inserting the pressing frame containing thematerial stack into a bath of hot-molten paraffin in a temporarycontainer 14 (Fig. 5). During this bath, the container is heated by theflame of an'ordinary Bunsen burner 15. In this step, the paraflincoatings on the sheets which yet remain as thin layers licti-x'a-ensheets in the material stack are completely liquefied. This heating bathis maintained for about twenty minutes, the temperature of the parafiinhol35 C. iiy the time the material-stack is thoroughly iwahwl, some ofthe moisture remaining with the parailin between the sheets inside thestack becomes vaporized and escapes from the stuck into the bath. Suchmoisture that which may have been entrapped in the coating parafiinduring the dipping and building operation when the parafiin was not atso high a temperature as in this bath, i. e., being then preferably lessthan 100 C.

Upon completion of the treatment of the material-stack in the heatinghath, it is subjected to the highcs; practicable mechanical compression,by some such means as that shown in Fig. 6. This is a very importantstep in the process. It results in substantially completing thesqueezing out of the thin paraffin layers between the sheets and therebywashing out from the interior of co-operatively with F ig. 7 where21.and 22-indicate the respective bunches of foil ends at the oppositeends of being particularly adapted forl.a sectional .condenser. Thesingle section of Fig. 7 however, may be permanently =clamped and usedas a .complete. condenser, forits air-tight conditionwith mica and foilsheets closely compressed together. adapts itfor such final use; In theassembly of ig 8. are provided. insulating barriersorseparators 23between 4 the-sections. These may be mica sheets.

ease temporary markers have beenused for the. sections j in; buildingthe inaterial-stack, these insulators23 simply replace such mar kers..In the assembly of Fig. 8 also, the sectionsare electrically connected.together by connections 24, .in the manner. long practiced for producinga. sectional "condenser (as shown), and, of course, .as. usual,theseparators 23 project onlyat one end of the con:

denser where the sections are at different po tentials .and requireinsulation from'on'e-aib other and where there are 110 connectionsbetween the sections. In practice, these connec 'tions 24. areconstituted simply-by" soldering together, adjacent bunches fo'f'toiliends. At

this point, if ny processes have been care: fully. followed, thecondition of each section willbe thesameas the condition of the com:

"pleted material-stack, i. e., each section isin such conditionihatitmight be used alone as a condenser. v Thesubsequ'ent .treatrnentf of theassembled sectional condenser-of, Fig. 8 (to be described in connectionwith Figs. 9 and 10) isthat simply-which is. desirable to put theassembly into the same said condition as is each section and. also toinsure the maintenanceof such condition as by a permanent embedding inp'arafiin. p y f Y In Figs. 9 and' lO (elevation and plan respectively)is'shown part of the apparatus for such further treatment, and in Fig.11 is shown a detail of the leaf spring employed.

In Figs. 9 and 10, the condenserstack 25, shown in dotted lines in Fig9, has been inserted in its final metal casing 26. At this stage, thecondenser has placedon its top its final stud plate 27. (Fig. 8), withhigh potential terminal or stud 26' mounted therewith and projectingupwardly, and conducting strip leads 41 connected to the foil-hunches ofoppositepotential staclesections as in Figs.

12 and 15. On top of the casing 26 is secured by screws a temporary head29, provided;

with a cross piece 30, (Fig 10) having a central opening up throughwhich projects the stud terminal 28. This serves to center the condenser25 in its casing 26; and this temporary head 29 ser'ves'to receive theparleaf spring 37, as shown in Fig. l1.

afiin which is afterwards filled in around the condenser in its casing.Theentire casing 26 is mounted in the press shown in Fig. 9, said pressconsisting of top and bottom plates 31 and. 32, held together by bars 33and 34 threaded at their ends and provided with nuts which hold theframe together. At the .center of the top member 31 is a screw 35 whichextends down through a threaded hole in top plate 31, and'is providedwith asuitable handle 36. 1 In series between the clamp screw 35 and thecondenser terminal 28 is inserted a This spring consists of two-leavesbolted together at their ends and drilled with the central holes 38 and39 to receive respcctively'the clampscrew 35 and condenser terminal 28..

. Thereupomby handle 36 thecondenser 25 is clamped against the bottom ofits casing 26, which restson the bottom plate 32 of the press. Thisspring clamping is an importantf'unction which will be referred to. Thisclamp is shown in side ele atien in Fig. 14:. By-mea'ns of the clampingin thispress, the same highest practicable coi'npr'ession is ob tainedon the assembled condenser as'was ini tially obtained by the clamping ofthe materialestack 6) and as was maintained on the material-stack and onits sections after rcmoval .of theclamp from the material-stack. Inother wo'rds, by means of the clamp of Figs. 9 andil the sections of theassembly are now compresed together with the highest practicablemechanical compression. The. condenser stack 25 in its casing 26 withclamp applied as shown in Fig. 9, is now subjecti ed to aprocess ofpre-heating preliminary to the embedding operation. As shown in Figs. 9and 10', the temporary head 29 is open at its top save for the crossmember 30 (Fig. 10), and has ,onlyside walls to constitute an.u.p-' wardextension of the side walls of -casing 26.

The process of pro-heating consists in pouring hot; wax throughsaid headdown into the space in casing 26 around the condenser 25, until'bothcasing and head'are filled; and thereafter, and while this parafiin isin the casingandhead the heat of a Bunsen burner fiame'is applied to thebottom of the casing (similarlyto Fig. 5) for the purpose of cooperatingin heating thoroughly the casing and condenser 25, this latter beingdone by playing the gas flame around the exterior of the casing. Thisgas flame may be applied to the casing prior to the pouring in of theparatlin, but if that be done care should be taken that such applicationbe not caress-ire on account of the-possibility of overheating andcarbonizing the parafiin'sheath or marginal paratiin around thecondenser, and of melting the soldered connections of the condensersections, which should not be heated as high as 150 C. I I

The hot parafiin in the casing serves to thoroughly heat the condenseritself, thereby condenser is thoroughly heated and itsseud para'ffinliquefied, the hezitingbath ofparafiin 1S pourecl out oflt'he easinghead 29, by an inuersion ofthe en reejgpa-rntus ofiFij 9 The condensernoiv readyifor its final parafiin-embedinent in: its c'q' sing, in aninstnnce wliene the ca sing, .to he provided with acovenseryingpiartof'a inennsto per nanentlyconipresjsjthe condenser within the ensing.

clamp small enou to enter t he jfi nal conense as g, sneer; ndepen e t Of the .cl singe si Permit ie use 9f", permanentclg np' 'in res l entform,, s ueh relkefihm n j SPJQXiilQlfok; he G9 edenser .1 foi-enliasheeni l, i c j st abort)? desqr 'tied,tlwtiislusih P r a ,spiii'ngclampiisjt i b enn l eli o t e condenser emerges-teeny t i laeeg he s'emcl'fcolil'fit 'penesi ym ae' iusukitiaigcoinn e s onlblhc'k 12,311M1i1!. b ttom.

com pressing block 4.3 i 1f ijc1rmeybQ. oifmetall. The to p insulilt-ihgblock lzgi'n ybe of; l; i,te or :1 Li y other suitable, insulator; whichwill, withstzuid the trealnncntiin'hot parnflihnniltl 1c 11 i gh;mechanical, compression involivcd'in n: y p rocesses, The fuont of thecondenser 25 shown.

in Fig, 12 isone ql ithesides oi; the assembly and ntwhich the seriesconnections are made and from which. pnejeetthevzs pntar iilg in;

u a sflifl; i'Fig- 8-. To. thelotlier twinned fiat sides of theondenser, e lthje, sides formed vo,f.the edges. ofthe. miizfiishefets,12).,m1e placed sgacing blocks Miami 4A of? insulating materials'imilzir to, thahoftop insulating, block These s de. sulat ng hloeks44and e lt seme to, 'keep thestack in al'inement and also to fill thespace'beneatl'i the high compression of the press before the $9 the P fi ting- 2 anflfii), f m s top nd the top block 42 zind to providesurfaces over which pass the wire 45, which constitutes the resilientclamp. This, wire consists n-eterably of piano steel wire and is woundtightly arounclthis assembly, as shownin Fig-'12;

while the assembly is maintained under the highest practicable,mechanical compression as-in any suitable temporary clamp or press,

such as aiC-clzunp, n visa, or any other suitable form of press, such,for exn'niple, :isthat shown in Fig, (3. While the assembly is under,such compression, the wire 45 is wound withflits turns tigl'itljlarou'nd the assembly audits ends fastened; securely to inein'tiiin sameis ren'iov edi'Tfhe'eileot"oi the windhig;

I V, l i I M A off'thiswire45is cuinul zitivqeach tti rn'ilddin g leeinsta e, hem Yer, w i sn; the corn. ,de'nser 18,110 beplovifded withaperinancnt to the efliect of the others inserYi-ng to increase the,tension on the assembly; The insulating; members 42, 44: and A lserve-t0 insulate the wire $5 from the and p revent electricnliconnection between 'the two e nds of the stack whi'clr'are efo'ppo'sitepotential The com: prc ssion on, the stack is, of course,longitudinalihetween the top insul'a't ing plnteego-11d the bottom,eonipression jp lnte 43;. above compression fliectcdWVhile the j'contleriser is cold; .l'hereuponthe condenser, with its sn nll' elgn npapplied, be 1-e1noved, 'fi oin the large press'i 'nditlr'oroughlyheated, in a. bath of, parafljn ,at' about:13 5 C.' for about twentyminutes the result being .to thereby hent the condenser and liquef-j themarginal, ara-fin IL andiabout the condenser. This heating bath isprel'irninziny to a further coin-j pression, but it also servesto driveout of'and' oil from the condenser any or moisture Whichmey ha vebeen'introduced into. the marginal sincethe production ofthe condenserfrom theniaierial steek or since the air and moisture werefirst-previously washed out from the materiel-stack. Pf theeohl'compression j'ust preyi'ous to ,thlis heating bath be omitted. i.c. ifthe condenser be subjected-to the healing bath without, beingunder. sirbstnntin l compression, then the Yzilne may be lost 01 theadvantages of the originnlliot comprcssion of the material-stack, ii 0.,the sub-, stnntiul washin out oi. 'fl.l1',.U)'ol moisture from betweenthe sheets in the interior oflhe stzn-k.v As the result olfrthis,heating bnlh, all the pornfii'n )fltl'clllililllllg in and about theeondenser (and ,ztt this stage there is. very little, if-ztny, parafiinleft inside the condenser) is lixpi'eli'ed'. The hot staclnyetsznlahurVshercafter under compression, is then removed fro n'..tl i e heatigboth end. returned to the P i lIl clfe i ijpv 0.1- erbor pr y the coinlressioiris egnin applied, but to a degree higher, than, when, theconclenscr was cold. lThijle under the high compression of the press theermenent small-clamp 4'5 is turther thghtenei, to maintain thecompression at. tained the large clamp or press, which at this stageshould have been set for about one thousand pounds per square inch ofactive area of the overlapping portions of the foil sheets in the centreof the condenser. Such increase of compression and the further tightening of the permanent clamp are permitted when at this stage there isany paraiiin remaining inside the stack as between the sections, suchparaffin being of course soft as the result of the heating bath. Uponthe tighte n ing up (or rewinding) of the small permanent clamp, thecondenser is removed from the large clamp or press. This operation,whichis the final operation on the condenser stacl-z itself, has resulted inyet more completely squeezing out any paratlin remaining between thesheets in the condenser and therefore in washing out any remaining airor moisture vapor within such parafiin. After the application of anysuch permanent spring clamp as in Fig. 12, the assembly of Fig. 12,which is the final complete condenser in an electrical sense, is placedin the casing 26 of Fig. 10, together with the temporary head 29 for thepre-heating preliminary to final embedding, which already has beendescribed in connection with Figs. 9 and 10; but the clamping appa ratusin Fig. 9 will not be needed now because the wire to of F ig. 12 alreadyserves to provide the high resilient compression of the leaf springclamp apparatus of Fig. 9. However. the top lead 40 (Fig. l5) may beconnected to the condenser terminal 28 (Figs. 12 and 15), the latterbeing centered through ,the opening in the head 29 of Fig. 9, in orderto center the condenser of Fig. 12 in the easing 26 of Fig. 9.

lVhether there be used in the process first above described inconnection with Figs. 9 and 10, the condenser of 9 with the temporaryleaf spring 37, or the condenser of Fig. 19. with a permanent resilientclamp as 45, for example, the effectof the. resilient compression duringthe healing bath in the casing 26 of Fig. 9 will he the same, i. 0.,when the condenser cxpands during the process of preheating in theparaliin bath in the casing at; of Fig. 9. the. resilient chimp willyield to prevent dcl'ormatiou of or injury to the stack, and at alltimes t'lurcnitcl during the. process (and tlnrren'ller in servi e inthe case of the permanent clamp of Fig. 12) the springciainp will yieidduring the lli the cox-ling to conform to the length of flu sla k and atall times uniformly exert the desired uniform high compression.

'lhcreupon, in the case oi the condenser of Fig. 9 or the condenser ol-Fig. 12, after the prc-lurating bath of parail'in of Figs. 9 and 10 ispoured oil from the casing 26, the assembly of the casing, condenser andspring clamp (i. 0.. either the temporary leaf spring clamp of Fig. 9 orthe permanent sgring clamp of Fig. 12) is inserted in the apparatus ofFig. 13 for the purpose of being subjected to the production of thepermanent embedment of the condenser in hot parafiin preliminary to thefinal stage of cooling. For this purpose one or more-of such assemblages(two as shown in Fig. 13) are placed in-tank 46, which is used primarilyas avacuum tank, tube 47 I ed the preceding parafiin heating bath and awhile the stack is yeta-s hot as possible, and the subjection to thevacuum treatment should also be effected immediately. This vacuum shouldbe a fairly higlrvaeu'um of the order of a few millimeters, atpreferablynot much higher pressure than 3 millimeters. The vacuum treatment neednot be applied to the stack for more than a -few minutes, because itdoes no good save while the stack is hot and its marginal wax isliquefied or soft, the obj ect of the vacuum treatment being to removeair and moisture from the liquid or softmarginal wax in preparation forthe process next to be effected, of enveloping the stack in hot.paraffim for eventual cooling and embedment.

All this time thestack is under the abovedescribed mechanicalcompression of either the leaf spring 37 of Fig. 9 or the permanentspring clamp 45 of Fig. 12. I

\Vhile the vacuum is yet applied to the condensers in the tank 4 6, hotparaflin for the permanent embedding is flowed in around the condenserin each casing until not only is the stack completely submerged in theparaffin, but the head 29 also,(Fi g. 9). ontop of the casing abovethelsta'ek is completely filled with the hot'parafiin', so that a fluidhead of molten parafiin is established above that part of the fillerwhich lies in the vicinity of the insulating portion of the casing andof the neighboring metal parts of the casing and high potentialterminal. The maintenance of the vacuum around the stack until thelatter is submerged in the parailin serves to prevent the entrapping ofany air or gaseous vapor in any portions of the final embeddingparallin, which may be so close to the condenser as to permit electricallosses or breakdowns in service due to such air or moisture. \Vhile thehot embedding parafiin is being flowed into the exhausted space aroundthe con-- denser, the air or vapor which may have been in the marginalparatlin of the condenser and which has been removed therefrom by thevacuum and attenuated and distributed through the vacnous space in thetank is prevented by the continuation of the vacuum from beingconcentrated or entering again into the marginal wax. Thus, the'inflowiug parafiin from pipes 49, branching from pipe 50, connected toparatlm reservoir 51, can, upon entering the condenser casings, mergewith the hot. marginal condenser parafiin freed of air and moisture, theincoming parafiin having been also freed of air and inois ion Ill)

eser oi 51. tank 6 condenser is, desired these processes o f yapnnm andfilling-in embedding .parefl n While under vacuum are extremelyimportant. I

An equalizer pipe-6 3 is connected between the wax reservoir 511411111the tank 46. Its

function-is to make theg'as pressure on wax in rcser-vrnrfil atwalltunes equal to tha t -1n tank 46, the reservoir 5ibeingpifoyidedwith anair-tightcover-'65. Then rega rdless o2 any application Qf'vacnn n(or-air pressnre) to;tan k 21-6., the. pein'ifml wil fle fi' em, we tatfect ngitliepperation'of'my-lprocesses.fl""

voir 7 51 into' the cond a $6 uml i Y i t hea g ven. by

tinsel n if? Vacuum v :ibnal nl t equ liz r Din G3ft 63' out of servicedesired, .v'alvefil being then turned to open the reservoir ,61

to the-atmosphere. The other or norinal posiion of valve si nply pl aces1n co nm nny cation with one anotherthe lair-spaces n At anytillipfitter tlielilfiowingparaliin has s bmerged he C ndens n -its easing.the vacn ni treatment can be terminated by] e lo. .i 1ig f al e 1 inthel uheft th f vacuum ,i lp, a d by, th qpeein eat-fli k e c' iwl e1211 thePiP atlt er sli ii em:

em. du ing the, p'ana fi fill es fl e -e i1.'enent or .vap or .which hascerneffrom the stack or innrjcating'withthe outside air.

incidentally fro rn the inflowing plarefiing,

tank 4 6 on account of the greatly rediieed pressure on theparai'fin-due to the acunni,

will haverisen up through the hotparaflin in the condenser easingtopointsat or near its surface, where it .n ay exist in the form of foamor iroth justbelow the surface. Thereupon these bubbles jnstbenea-th thesurface will-break through the surface and disappear in thespaee in thetank. Therefore; it is preferable not to shut off the main paratiinvalve 53 until afterthis frothhas disappeared and. therefore until allerboth the casiru and the head 29 are completely filled with paraffinSllbbiillltlilli) freed of air. Prelerably also the wire 52 is notopened to let the outside air intotanli d6 nntil eifter saidfilling hasbeen completed.

After main paraffin valve 53 has been closed, and hefor e'blceder alve52 is opened,

and 'before paralfin has solidified in pipes.

49, Valve fl-is opened inpipe (the end of which is open toitheatmosphere), in order to causeatmospheric pressure to force paraffi ireniaining'in pipes 419 against-therednced helcl i tie le t reservoir 51above tank 46.1 llnis; the m a fin may flow by gravity 'f en ese -Y0i. f51f to the condenser x,caminfgs 151,6, "i rtefl pr Ct-iv 0f the ai prssiu-eln the lett r? HID" *iplaee i= new;

'Il drtaizit in'anycaisew he're' 'i erl-t i hav t e 1 d holosteric,i.effreed fofell. birds I lhi s"p1:oc css" consists ein ffcertaiii reatrnent xirliieh" is applied daring ofthepiraf fi'n inside the casing-26nndhead.a29; This treatment consists; fgenerally speaking, in li y egih He e d n i mifi emi bottorn ;np\i ards '1; "e; the bottoni more"theitop zill "a, p q ive'i enne- E l s ay'rhmfi e either y "("1)"etreizfi n f etfi 'th' 1 tom without nythin to the topparal';

o lpwa s lb wmfi mp rt f r- 3*) y ab an i, iii ti t m"e' i 1m h p ly ghe;

;Si eny; we latter isP'r'ef 'rabIe' f r'beonpi fof "time and n'e li ttlo 'e the s i e ii tibn of the ;process. In pract1ee,jthe "last orpreferable manner has heenleffeictedhy i n. sorting the condensereas'ing26 inv a shalle W pan or tray 55 Containii g nater, which may be renewedfrom tinie'to time; or (consists of water circulation. Alternatively andpreferably, an air blast; from blower 56 1nay be directed againstthelower portions of the sides and the b ottorn of casing 26 in the absenceof Water tray 55. The air blast may be directed against the desiredlower portions of casing 26 by means of flexible tubing 57. And, as partof said preferred .manner of ex ecuting the process of gradual coolingfrom the bottom upwards, the npper part of the liquid paratlin bodyfincasing 26 andhead29 may be and has beensuccessfiilly in practice, heatedas by-peuringin additional hotpal-at fin f om. tim to imelwhk'h," ind d,i useful also to con pensetefor the shrinkage of the parattin in thecasing as its contracts due to its-temperature being lowered and to itssolidification. 'The heating is elfected eddi: tionally, when desirei hyneans ota removable eloctrical heating coil 58 mounted circ mferentiallyaround head 29; or alternatively with'such coil the flame of a Bunsenburner maybe played around the walls of head '29. and around the upperpart of casing :26. I

In Fig, 14 is represented in dottcdlines the condenser with all of thetemporary clam ping apparatus of Fig. 9, including the leaf sp r ing3'(j but whenthe permanent spring ela 1 np of -,Fig. 12is used,.suchtemporary apparatus willnot be used, and the appai atus subjected to thecooling treatment of Eig. 14 will consist simply of the condenser casing26 containingcondenser 25 in ifs'spr'ing clamp 45 of Fig.12, andthetcmpora yhead 29, heatingcoil-58, and any of the described means forabstracting heat from thelowerlportion of the liquid paraffin in thecondensercasing, and adding heat to the top.

The importance ofthis cooling treatmentgradually from the bottomupwards, particularly in connection with the head 29 on top of easing26,: or of. the equivalent of this pro s's'is due to the fact that thecooling of paraffin or any substantial equivalent waxes whichpcanbe usedfor these condensers is accompanied bya large decrease in volume,suclrthat without this process an ordinary ornniform cooling from allsides would resultgjirst the cooling. of an exterior shell andthe?cooling and contraction of the i11- tei'iorfvv hich would result inthe formation of interior voids or cracks, which, in turn, might befilled with gases or vapors which had been entrained'jnthe paraffin orwith atmosphere drawn urn-om outside the paraffin; and such ordinaryprocessof solidification or freezing would result, as ordinarily, in thedriving away from the surfaces of solidification towa rd the' centralliquefied portions of all foreign materials, this central portion in thecasingof a condenser being the stack itself, from which it is extremelydesirable that all such foreign materials be removed as far as possible.With my process of cooling gradually from the bottom upwardly, the aboveaction is avoided and on the contrary the surfaces of solidification,gradually moving upwardly, drive. before them all such foreign materialsand, not only that, but force them up beyond the vicinity of the upperor high potential end of thecondcnscr and out of the casing 26 entirelyfurther up into the paraflin contained in the head 29. Hence, thepermanentcmbedding paraffin in the casing (as distinguished from thetemporary paraffin in the temporary head 29) is made substantiallysolid. and voids otherwise tending to become fixed in the upper part ofcasing 26, in the neighborhood of the upper or high potential end of thecondenser, are caused to be established, if anywhere, in the temporaryparaffin in the temporary head 29. Also, the use of head 29 inconnection with the repeated addilion of hot mraffiu to compensate forthe shrinkage during cooling, prevents the formation of a finaldepression in the paraffin in the top of casing 26, so that the finalcooling of the top of the paraffin in the casing results in a uniformmass of paraffin free from any lines of cleavage which might exist inthe parafiin in the casing if it were allowed to solidify with adepression in its top surface and if after solidification additionalparaffin were added to fill up the depression.

Upon the application of this solidification process, the paraffincommences to silidify at the bottom of the casing andat lower portionsalong the sides of the casing and the sides of the stack resting on thebottom-of the casing 26, the rest of the paraffin in the casing26 andhead29'remaining liquid. As this cooling process iscontinued (which maybe severalhours, depending upon the size of the condenser and dependingupon the particular meansfor cooling and heating employed, the air blastabove described being more efficient than the water cooling), thesolidification extends h1gher.up from thebottom of the casing and stillhigher up inside the sides thereof and along the sides of the condenser,so that the remaining liquid paraffin is U-shaped in cross-sectionaround the condenser.- Thus, as the solidification gradually extendsupwardly, the liquefied r mainder at all times bears down u on andagainst .the upwardly moving sur aces of solidification and directlyfollows up the shrinkage or contraction at such surfaces accompanyingthe solidification, to the end of preventing voids or cracks..-Meanwhile, as stated above, the surfacesof solidification driveupwardly any remauent air or moisture, not only to the upper part-of thecasing 26, but up into the head 29. If'the head 29 be sufficiently highto contain a sufficient volume of paraffin, then all the air andmoisture as well as voids finally forming near the upper surface of theparaflin will be contained wholly within the head, so that when laterthe temporary wax in the head 29 is cut off, there will be left novoids, air holes or depressions in the upper part of the casing in thevicinity of the condenser. In instances when the execution of thiscooling process involves specifically the ap lication of heat (as in thepreferred form) to the paraffin in the head 29, such application of heatmay be discontinued after assurance is obtained by observatirm thatsolidification has been COlllph-ted of all the paraffin within thecasing 26. It is to be understood that this cooling operation isconducted under at least atmospheric pressure, so that the atmospherehas access to the top of the molten paraffin in head 29, in order toassist in the cooling process in respect of the prevention of voids inthe paraffin in casing 26. If desired, this air or gas pre sure o top fthe molten paraffin body may be greatly increased above atmosphericpressure, this increased pressure being advan tageously as high as 1-50pounds, which can be maintained until complete solidification has beeneflected. The effect of such increased pressure is to com press anyvoids or bubbles in the pa rafiin. thereby making their effect lessdeleterious. For this purpose, the condenser in its filled casing may beleft in ianlr- 16 of Fig. 13 for the execution of the cooling process,and con'lprcsscd air from asuitable pump may be introduced into the tank46 hy'way'of valve 52. Also, the application of additional wasinto thehead 29 during the cooling process may be effected by way of thepipes'49'irom the paraflin reservoir 51, in which case, of course, theparaffin in reservoir 5-1 shouldbe subjected to at least tl'iesa'megaspressure as-that of the tank 46 by way of val-ve-645, in-order to permitthe inflow of paraflin intotank 46.

Throughout the above paraffin embedding process and'ever'since-thecondenser stack has been assembled,- it has'beenunder the highestpracticable mechanical compression either by way of atemporaryrigid'clamp, a temporary spring clamp or a permanent spring clampadapted to be received'w'iththe'staclt into the final condenser casing.If thefclamp be a temporary el'ainpas illustrated in Figs. 9 and 14, itisre'move'd upon the complete solidification of-the embedding parafiih;but when such temporary clamp is employed and duly removed, itsliould'be replaced with the clamp which is to be permanently assembledwith the condenser in service, as soonas possible after the removal ofthe temporary clamp; for even although the embedding paraffin becompletely solidified before the removal of the temporary clamp, suchsolid paraffin is liable to cold flow and, therefore, is liable topermit expansion of the stack under heating conditions which may beencountered in service. andthis-should never be permitted. For thisreason, it is preferable, as stated above,- to employ some such form ofpern'ia-nent' cl'amp as that illustrated in Fig. 12. or anot her form ofspringclan'ip such as that. shown in my application, Serial No. 292,126,filed April 23, 1919; of which the present application is acontinuation-in part, and such permanent clamp should be applied to thecondenser at'the-earliest possible stage in the process, even at thestage when the stack has been treated to the parafiin bath as in Fig. 5,just before it is subjected to the washing out processillustrated inFig. 6.

\Vith' further reference to Fig. 14'. After thesolid-ification ofparafiin is completed, the head 29 is removed from the casing and fromthe paraflin in the head above the casing, this removal being readilypermitted upon the applicatioirof heat from removable heater 58 cr'of agasfiame tothe outside of the walls of head 29; Then, by means of a longknife applied to the condenser any suitable meansof permanently clampingit in its casing; for

example, a construction may be provided whereby the application of acoyei to the top of the casing' will serve in any well lmown manner tocompress the condenscriiithe cas ing. Preferably, however, as when apermanent small clamp (as in Fig.' 12) is em ployedin the processes,such permanent'clam'p (as '59, Fig. is left on thecond'enser in thecasing and any suitable cover '60 is applied to the top of the casingover the embedding parafiin. The modified form of small permanent clampin the casing, which is shown in Fig. 15, comprises a' U shaped steelyoke 59 which elnbraces'the condenser. The U cnd is insulatedfrom thecondenser as by a: stack of mica sl1cets 62. Two of these clamps aredisposedsymmetrically on the condenser. The two ends of each clan'ip areentered by adjusting screws 61 which pass up through a steel springplate 43* (common to both clan'ips), whereby plate 43"? is flexed toapply the desired compression. Mica stat-E662 is placed on top ofinsulating'plate' (3ft (as of balielit'e) which in turn rests onf metalplate 27 which transmits the pressure of Insulating the clamps 59 to thecondenser. plate 66' insulates the lead from the top of the condenser)The condenser terminal 28 is'soldered atits bottom to the upper end ofstrip lead 40. l

The condenser terminals may be brought out through the casing "in anydesirable or well-known manner-as (Fig. 15) the high potential terminal28 through'an opening in insulating cover and one terminal (that of lowpotential) may be constituted" by the metal casing 26 itself. pursuantto the common practice.

The above advantages of the embedding and cooling operations may beobtained, it desired, by providing a threaded opening'it) and a plug 71therefor in the bottom of the casing for the inflowing of embeddingparafiin, the casing (with its final cover applied and connection orconnections made therethrough) being inverted during the filling andcooling operations, and after solidification, the bottom opening closedup. By such an operation, one may avoidthe use of the temporary head 29(Fig. 9), for the condenser would be centered in its casing by assemblywith the cover of therasing (Fig. 15) the assembled condenser and coverbeing applied in and to the casing; and the filling of the space in theinverted casing produces an even higher fluid'head on thefiller in thev1- cinity of the higlrpotential insulating portion of the casing thanis obtained by temporary head 29 of Fig. 29. Thus, with the casing withcover applied (Fig. 15), but inverted during filling and solidification,and the high potential terminal-end of the coir denser (top Fig. 15)lvin'g in'what is temporarily the bottom of the container of liquidparaffin (Fig. 14),}1'nk1 the-supply of heat to the upper portion "ofthe tiller, the paraffin begins to cool at the bottom around 'the'highpotential end of the "condenser, and the parafiin thereabove bears downon the upwardly extending surfaces of solidification, therebypreventingthe formation'of voids or cracks near the high'potential end;and anycra'cks' or' voids in the. paraffin 'near the lowvpotentialendiof the condenser would be relativel "innocuous. "Al-so theparaffin by this met 0d is caused to adhere to the inside surface of thecover'of a casing, as the result of being applied thereto when hot andmolten. This condition of the insulatingwax at the neighboringcondenser/portions of high potential differenc'e a's'sists in'preventingelec'* trical' brushing, freduces the tendeney to creepage and preventsabsorption" of moisture at locations where :mois'turei would produceserious resultsf H YVhen a ermanent condenser clamp is rope'rl'yfandpermanentused' or the st'acli is lyicla mped'iiiside e'casing any means,it is not soj'impor'tant that the foil sheets be non iiesilient, forsucli'c lamp' at a fsufiiciently early stage inthe process willserve tomain; tain the' desired intimacy of contact between mica and foilsli'eetsfwhich excludes, everything foreign from" between the 'slieets.And even when a permanent eondenserclamp be not'used, the foil sheets'mayhave some de gree of resiliency with-out resulting inbreaking downthe hermetical sealing by the marginal she'atli' parafiinfespecially ifthe stack in 'th'e earl ta'ge's of the process have a sufficientthickness ofn ai g'iual sheath to prevent expansion "of the stack'(laterally with respect to the stack), and this may be obtained ifnecessary by suitable dipping in the paraffin bath fort-he purposeofohtaining such substantial thickness of the marginal paraffin.

\Vhenevcr compression or clamps are refcrred to herein, such compressionis to be understood to he the highest mechanical compression which ispracticable to be applied on the soft lead-foil sheets, and this inpractice is about 1,000 pounds or more per square inch of the activearea of'each mica sheet, i. 0., that part of the mica sheet which liesbetwecn theovcrlapping 'foil sheets, this being a pressure which amountsto about 'a ton or more on the entire end surface of an ordinarycondenser 3"lliig'h by 2 long by 1%" wide.

\Vhen the word paraffin is used in the claims, it is intended asapplying to any material which is the substantial equivalent of theparafiin-carnauba mixture preferred herein. As to the limitation tosheets of mica, it is to he understood that this does not exclude othermaterials which might be. found to be equivalent within the invention.as to the valuable properties of mica for this purpose involving its lowdielectric losses, its nonporous character, its ability to be formedinto thin sheets of sutiicient mechanical strength for my processes, andits high di electric constant which permits production of a highcapacity condenser of small volume.

I claim l. The method of making an electrical condenser stack ofnon-porous dielectric sheets and metal sheets which consists in firstcoating the active non-porous surfaces of the sheets, prior to stackingthem together, with a dielectric detergent liquid; thereafter stackingthe sheets; and thereafter employing the detergent layers between thesheets in the stack to Wash out air or mo sture from he tween thesheets, by squeezing the sheets together when the detergent layers areliquid, thereby forcing out said layers with any entrained air ormoisture from between adjacent sheets and permitting the non-poroussurfaces of adjacent pairs of sheets, so freed of air and moisturebetween them, to lie together in intimate surface contact with oneanother in the stack.

I 2. The method of making an electrical condenser stack of non-porousdielectric sheets and metal sheets which consists in causing the sheetsto {adheretogether" during the stackingloperation by'first coating theiractire non-porous surfaces, prior-to stacking, with normally soliddielectric detergent in hot' inoltencondition thereafter 7 stacking thesheets't-ogether when the coating on at least one of the facing surfacesof two adjacent sheets is warm enough to cause adherence of suchsurfaccsi' and subsequent to stacking, employing the detergent layersbetween the shects in the stack to wash out air or moisture from betweenthe sheets. b squeezing the sheets together when the detergent layersare liquid.'thcreb "forcing out said layers with any entraincf l' air ormoisture from between adjacent sheets and permitting the non-poroussurfaces of adjacent pairs of sheets, so freed of air and moisturebetween them. to lie together in'intimate surface contact with oneanother in the stack.

The method of making an electrical condenser stack of non-porousdielectric sheets and metal sheets which consists in cansing thenon-porous surfaces of adjacent stack sheets to adhere togethertemporarily during the stacking operation. by first coating the activenon-porous surfaces of individual sheets, prior to stacking themtogether, with a normally solid dielectric detergent in hot tut)moltei'i condition, and then stacking such sheets together before saidcoatings on the facing surfaces of pairs of adjacent sheets beingstacked together have cooled and solidilied; and, subsequent to suchstackin em ploying the detergentlayers to wash out air or moisture frombetnveen the stack-sheets, by squeezing the stack-sheets together whenthe detergent layers are in heated liquid condition thereby forcing outsaid layers with any entrained air or moisture from between adjacentsheets and causing the non-porous surfaces of adjacentsheets, so freedof air and moisture between them, to be squeezed together in intimatesurface contact with one anotherin the stack. s t H I 4.- The method ofmaking an electrical condenser stack of non-porous dielectric sheets andmetal sheets which consists in first coatingthe active-nonporoussurfaces ofthe sheets, prior to'stacki-ngthem' together, with anormally. solid dielectriodetergent in hot molten condition;- thereafterstacking the sheets together; and, subsequent. to such stacking,employing the detergent layers between the sheets in the stack to washout air or moisture from between the stack-sheets, by squeezing, thestack-"sheets together when the detergent layers are in heated liquidcondition, thereby forcing outsuch layers with any entrained air ormoisture from between adjacent sheets,,and causing thenon-poroussurfaces of adjacent pairs-ofsheets, so freed of airand moisture betweenthem, to be squeezed together in intimate surface contact withoneanother in the stack. w j V 5. The method of makingan electricalcondenser. stack of non-porous dielectric sheets and metal sheets whichconsists in first coating the active noneporous surfaces of the sheets,prior to stacking them together, with a normally solid dielectricdetergent in hot molten condition; thereafter stacking the sheetstogether; causing the coated sheets to adhere to one another during thestacking operation and preventing unnecessary thickness of detergentlayers in the stack, by applying heat to the stack during its buildingthereby maintaining in liquid condition the detergent layers in-thegrowing stack, causing excess detergent material to be squeezed out frombetween lower earlier stacked sheets of the growing stack by the gravityof upper later stacked sheets; and, subsequent to such stacking,employing the detergent layers between the sheets to wash out air ormoisture from between the stack-sheets, by squeezing the stack-sheetstogether when the detergentlayersare in heated liquid condition, therebyforcing out such layers with any entrained air or moisture, from betweenadjacent sheets and causing thenon-porous surfaces of adj acent pairs ofsheets, so freed of air and moisture between them, to be squeezedtogether in intimate surface contact with one another in the stack.

6. The method of making an electrical condenser stack of nonporousdielectric sheets and metal sheets which consists in first coating theactive non-porous surfaces of the sheets, prior to stacking themtogether, with a normally solid dielectricdetergent in hot moltencondition; thereafter stacking the sheets; removing some of the air ormoisture entrapped in the layers of detergent between the sheets bysubjecting the stack toa s'uflicicntly prolonged bath in-hot moltendielectric material and thereafter squeezing the stack sheets togetherwhen the detergent layers are in liquid condition until such layerswithany remaining entrained air or moisture have been forced out of thestack and formed ,into' a thin sheath of cooled andsolidified dielec-vtric material around the edges of the sheets and the sides of the stack,said solidified sheath holding the sheets together the stack in intimatesurface contact with one anotherafter the removal of thedetergeritlayers from between them and after the dis continuance of the squeezingout pressure.

7. The method of making an electrical condenser stack ofnon-porousdielectric sheets and metal sheets which consists in first coating theactive non-poroussurfaces of the sheets, prior tostacking themto'gether, with a normally solid diel'ectric detergentin hot moltencondition, thereafter stacking the sheets; thereafter washing out air ormoisture from between the non-porous stacks of the resulting. stack bysqueezing the stack sheets together when the detergent layers are inliquidcondition, thereby forcing out the deter out, with any entrainedair or mois: turqfrom between adjacent sheets and causing the non-poroussurfaces of adjacentsheets, so freed of air and moisture between them,to be; squeezed into intimate surface contact with one another in thestack; said squeezed out detergent dielectric forming in a thindielectric sheath around the edges of the sheets and the sides of thestack; and continuing said squeezing operation until said dielectricsheath is solidified by cooling sufliciently to hold the sheets in-theirintimate surface contacts independently of such squctming.

8. The method of making an electrical-condenser comprising, a stack ofnon-porous dielectric sheets and metal sheets enclosed in a casingwhichconsists in first coating the active non-porous surfaces of sheets,prior to stacking them together,-with a normally soliddielectric deterent in hot molten condition; thereafter stac ing the sheets, thereafterWashing out air or moisture from betweenthe non-porous stack sheets bysqueezing them together when the detergent layers between them are inliquid condition thereby forcing out said detergent, with any entrainedair or ltlt) moisture, from between adjacent sheets and causing thenon-porous surfaces thereof, so freed of air and moisture between themto be squeezed into intimate surface contact with one another in thestack; said squeezed-out detergent forming in a thin dielectric sheatharound the edges of the sheets and the sides of the stack; continuingsaid squeezing. until said dielectric sheath has solidified by coolingsufficiently to hold the sheets in their intimate surface contactindependently of the squeezing; discontinuing the squeezing; placing thedielectric-sheathed stack in an enclosing casing, spaced from the wallsthereof and under high mechanical compression in the casing; softeningsaid-dielectric sheath in the easingby. heating; subjecting the entireassembly while said sheath is soft, to vacuum; and, while continuing theapplication of the vacuum and the high mechanical compression, pouringhot molten normally solid dielectric as a filler into said space,thereby removing air or moisture from the sheath and maintaining theintimacy'of surface contact of the sheets when the molten filler meltsthe sheath and until the entire dielectric filler has solidified as anembedment of the stack.

9. The method of making an electrical condenser comprising a stack ofnon-porous dielectric sheetsand metal sheets enclosed in a casing whichconsists in first coating the active nonporous surfaces of the sheets,prior to stacking them together, with a normally solid dielectricdetergent in hot molten condition; thereafter stacking the sheets;thereafter washing out air or moisture from between the non-poroussheets of the stack by squeezing-the stack sheets together when thedetergent layers between them are in liquid condition, thereby forcingout said layers and any entrained air or moisture from between adjacentsheets; continuing such squeezing until the squeezed-out detergentdielectric has cooled and solidified in a sheath around the edges of thesheets and sides of the stack having the ability to hold the sheets intheir intimate surface contact caused by the squeezing out of thedetergent, air and moisture; discontinuing the squeezing operation whensaid dielectric sheath has cooled and solidified to hold the sheets intheir intimate surface contact; placing the stack in a casingproportioncd relative to the stack to provide a space between stack andeasing; pouring hot molten normally solid dielectric into such spacethereby melting the dielectric sheath around the stack, whilemaintaining the stack under high mechanical compression in the casingand thereby maintaining the sheets in their intimate surface contactsafter the melting of the dielectric sheath.

10. An electrical condenser comprising a stack of sheets of non-porousdielectric and metal sheets and a casing enclosing such stack andproportioned thereto to provide a space between the sides of the stackand the casing, said space being filled partially with a sheath ofnormally solid dielectric material around the stack, leaving theirsurfaces in intimate contact with one another; and said space beingfurther filled with a comparatively thick mass ofnormally Soliddielectric material; said two masses of dielectric material beingsolidified together and constitutingv a permanent embedment of the stackin the casing; and means holding the stack under high mechanicalcompression in the casing, thereby maintaining the intimate surface.contact of the stack-sheets during the solidification ofthe entire massof dielectric in the space between the stack and easing.

'lLThe method of making an electrical condenser stack of nonorousdielectric sheets and metal sheets whic consists in cansing thenon-porous surfaces of adjacent stack sheets to adhere together duringthe stacking operation, by first coating them, prior to stacking, with adielectric detergent in hot molten condition; thereafter stacking thesheets when the coatings are in adherent condition; subjecting theresulting stack to a bath in hot molten dielectric; washing out air ormoisture from between the non-porous stack sheets by ,sequeezing themtogether when the detergent dielectric layers between the sheets are inliquid condition, the squeezed-out dielectric bein thereby formed ,intoa sheath around the e( ges of the sheets and the sides of the stack,which is able to hold the sheets in intimate surface contact afterdiscontinuance of the squeezing operation; discontinuing the squeezingoperation; placing the sheathed stack in a casing proportioned toprovide a space between the stack and the casing; and pouring hot moltendielectric material into said space, thereby melting said dielectricsheath, while maintaining the stack under high mechanical compression inthe casing holding the sheets in intimate surface contactafter meltingof the dielectric sheath and during the solidification of the dielectricin said space.

12. The method of making an electrical condenser stack of non-porousdielectric sheets and narrower and longer metal sheets, which consistsin first coating the active non-porous surfaces of the sheets, prior tostacking them together, with a dielectric detergent liquid; thereafterstacking the sheets, placing the metal sheets in positions wherein thoseof opposite polartiy project out from different portions of the stackand elsewhere are spaced inwardly of the edges of the dielectric sheets;mechanically holding the edges of the stacked dielectric sheets tomaintain them in common :ilinement in the stack while squeezing all thesheets together, thereby squeezing out the detergent layers and anyentrained air or mois ture without disturbing the stacked relation ofthe sheets to one another by the squeezing operation.

13. The method of making an electrical condenser stack of non-porousdielectric sheets and narrower and longer metal sheets, which consistsin first coating the non-porous surfaces of the sheets, prior tostacking them together, with a dielectric detergent liquid; thereafterstacking the sheets, placing the metal sheets in positions wherein thoseof opposite polarity project from different portions of the stack andelsewhere are spaced inwardly of the edges of the dielectric sheets;n'icchanically holding the edges of the stacked dielectric sheets tomaintain them in common alinement in the stack while removing some ofthe moisture from the detergent layers by submerging the stack in hotmolten dielectric material.

14. The method of making an electrical condenser comprising a stack ofnon-porous dielectric sheets and metal sheets enclosed in a casingproportioned to provide a space between stack and casing, which consistsin first coating the active non-porous surfaces of the sheets, prior tostacking them together, with a. dielectric detergent liquid; thereafterstacking the sheets, forming layers of detergent between the sheets;thereafter sqncezing out the detergent layers, when in liquid condition,together with any entrained air or moisture, from between the sheets.permitting the sheets to lie together in intimate contact with oneanother within the stack; thereafter placing such stack in the casingwith its high potential portion near an opening in the casing, the stackbeing held under high mechanical compression in the casing; and thenpouring a hot molten mass of normally solid dielectric material intosaid space and maintaining a fluid head of said material acting in thevicinity of high potential portion of the stack and the casing opening,to cause holostcric solidification oi the moltcn filler in saidvicinity.

15. In the art of making mica condensers, the process consisting inbuilding a condenser stack of sheets which first have been coated withparaifin before stacking; removing some of the moisture from between thesheets and the stack by liquefying the paratlin coatings by immersingthe stack in hot molten parafiin squeezing the liquid parafiin and anycontained air or moisture from between the sheets of the stack by theapplication of high mechanical pressure across the stack ends; andcooling the stack while maintaining such squeezing-out pressure, therebysolidifying the paraffin adhering to the sides of the stack on the edgesof the sheets.

16. The method of producing mica and foil sheet condensers having cleanactive surfaces of the sheets, and keeping the same clean, whichconsists in building a stack of such sheets each first coated withmolten parafiin before stacking, and keeping the growing stack warm andthe coatings therebysoft during the stacking operation; subjecting suchstack, with liquid paraffin layers between the sheets, to highmechanical compression, thereby squeezing out said layers with anyentrained air or moisture and causing the sheets to lie in intimatesurface contact with one another; placing such stack into a permanentcasing and under high mechanical compression therein, with the edges ofthe stack sheets spaced from the casing; and filling such space with hotmolten )araflin.

17. The process of building mica and foil sheet condensers whichconsists in piling such sheets on top of one another face to face in astack, dipping each sheetin molten paraffin before pacing it in thestack; utilizing the weight of the upper part of the growing stack tosqueeze out some oft-he paraffin from between the sheets of its lowerpart, by keeping the sheets coatings molten during building by the.application of heat to the stack additional to the heat of the warmcoatings of freshly stacked sheets; and finally solidifying the paraflinbetween and at the edges of the sheets thereby causing the sheets toadhere to one another and permit convenient handling of the stack infurther treatment without impairin" its unitary character.

18. he process of buildin a series-sectionat high potential mica andfoil sheet condenser which consists in piling such sheets on top of oneanother face to face in a stack, first dipping each sheet in moltenparaffin before placing it in the stack; placing section selparators ontop of each section of desired e ectrical capacity; utilizing the weight.of the upper part of the owing stack to squeeze out some of the para nfrom between the sheets of its lower part by keeping-the sheet coatingsmolt-on during building, by the application of heat to the stackadditional to the heat of the warm coatings of freshly stacked sheets;and finally solidifying the paraffin between and at the edges of thesheets, thereby causing the sheets to adhere to one another and topermit convenient handling of the stack in further treatment withoutimpairing its unitary character.

19. The method of making an electrical condenser stack of non-porousdielectric sheets and metal sheets which consists in first coating theactive non-poror surfaces of the sheets. prior to stacking themtogether, with a normally solid dielectric detergent in hot moltencondition; thereafter stacking the sheets; thereafter, when the layersof detergent be tween the stack sheets are cool and solid, ap plyingheat to the stack to melt said layers; and, while said layers aremolten, employing them to wash out air or moisture from the interior ofthe stack, by squeezing them out as vehicles for conveyance of entrainedair or 'I O l

